1. Field of the Invention
The present invention relates to a heat exchanger in which a condenser and an oil cooler are provided in parallel between a pair of headers.
2. Description of the Related Art
Conventionally, there is known a-heat exchanger in which a condenser and an oil cooler are integrated, for example, as shown in FIG. 4. The heat exchanger shown in FIG. 4 is disclosed in U.S. Pat. No. 6,793,012 and it has a pair of a first header 13 and a second header 15 that are disposed in parallel and oppositely and, between the pair of the headers 13 and 15, there are provided; a first tube group 17 that is comprised of six tubes and that is used as a condenser; and a second tube group 19 disposed above the first tube group 17 that is comprised of two tubes and that is used as an oil cooler. The first tube group 17 has: three forward tubes 17a through which a refrigerant flows from the first header 13 to the second header 15; and three backward tubes 17b through which the refrigerant flows from the second header 15 to the first header 13. Thus, the refrigerant injected through a refrigerant inlet 21 provided in the first header 13 travels through the forward tubes 17a to flow into the second header 15, and then travels through the backward tubes 17b to be discharged from a refrigerant outlet 23 provided in the first header 21. On the other hand, the second tube group 19 has: a forward tube 19a through which an oil passes from the second header 15 to the first header 13; and a backward tube 19b through which the oil passes from the first header 13 to the second header 15. Thus, the oil injected through an oil inlet 25 provided in the second header travels through the forward tube 19a to flow into the first header 13, and then travels through the backward tube 19b to be discharged from a discharge port 27 provided in the second header 15.
In such heat exchanger 11, the first tube group 17 and the second tube group 19 have different uses, and therefore the flow rate, flow speed, pressure and the like of the passing medium differ between the first and second tube groups 17 and 19. Therefore, the first and second tube groups 17 and 19 have different tube diameters, wall thicknesses and the like and, as a result, tubes of two types have to be prepared. Further, correspondingly, tube holes of two types have to be formed in the headers, and therefore there is a problem in that more man-hours are required and the cost is increased.
Further, the first and second tube groups 17 and 19 have tube holes of different pitches, and therefore two sets of jigs have to be prepared so as to form the tube holes and insert the tubes into the tube holes and, as a result, there is a problem here also in that the cost is increased.
On the other hand, Japanese Unexamined Patent Publication No. 2004-239598 discloses a heat exchanger 33 that is provided with a return pipe 31 disposed above the second tube group as shown in FIG. 5A. However, in the typical heat exchanger, a core 35 comprised of the tubes and fins has to be compressed before brazing the tubes and, for that purpose, a wire W is wound around the core 35 as shown in FIGS. 5A and 5B. At this time, there is a problem in that corners of the return pipe 31 may be crushed, as shown in FIG. 5B, if the winding force is too large.